Recycling spent LiNi1−x−yCoxMnyO2 cathodes to efficient catalysts for the oxygen evolution reaction

Abstract

The wide application of lithium-ion batteries (LIBs) for electric vehicles forebodes a future decommissioning tide of spent LIBs. Therefore, the recycling of spent LIBs has garnered significant attention, primarily due to the scarcity of resources and the detrimental effects of environmental pollution. However, traditional recycling technologies such as pyrometallurgy and hydrometallurgy methods are limited by their high energy consumption, high pollution, and complicated separation processes. Herein, we propose a novel and general approach to convert a series of spent LiNi_1−x−yCo_xMn_yO₂ (NCM) cathodes into Ni–Co–Mn hydroxide (NCM-OH) catalysts for the oxygen evolution reaction (OER) using deep eutectic solvents to extract valuable metals, followed by an in situ precipitation process using oxalic acid and a final self-templating process in an alkaline solution. The NCM-OH catalyst obtained from the spent LiNi_0.33Co_0.33Mn_0.33O₂ cathode is found to possess a nanoflake-assembled microrod structure with a large surface area (385.8 m² g⁻¹) and high porosity, which is endowed with abundant active sites and gas channels for the electrocatalytic reaction and mass transfer process. As a result, the NCM-OH catalyst for the oxygen evolution reaction exhibits a low overpotential of 273 mV at a current density of 10 mA cm⁻² with a Tafel slope of 50.46 mV dec⁻¹ as well as satisfactory stability. The effect of the composition on the catalytic performance is also evaluated by comparing different Ni_1−x−yCo_xMn_y hydroxide catalysts derived from commercially prevailing spent cathodes. This work provides a promising strategy for recycling spent LIBs into electrocatalyst materials for the OER.